This invention relates to coated abrasives such as abrasive belts and discs, and particularly to curl-resistant coated abrasives that are particularly adapted for use in applications in which the material is subject to very high levels of stress during use.
The applications for which these coated abrasives are designed are those in which excellent non-directional strength properties and the ability to absorb sudden stresses during use are important. An example would be an abrasive disc adapted for coarse grinding applications. It is foreseen however that the coated abrasive might also have applications in forms other than such discs.
Referring specifically to abrasive discs for the purposes of illustration, coated abrasives should preferably have isotropic physical properties, particularly tensile strength, in all directions in the plane of the disc. For the purposes of this application a tensile strength variation in the plane of the disc of not more than about 30% is considered "isotropic" and a disc with a tensile strength variation in the plane of the disc of not more than about 10% is considered to be "highly isotropic".
Discs for typical heavy duty grinding purposes should also preferably have the capability of absorbing impact energy such as might result if the edge of the disc is snagged and should exhibit dimensional stability, that is they should not warp or curl when heated or cooled or subjected to varying humidity conditions.
In the past this application niche has been occupied by coated abrasives using a vulcanized fiber backing material which exhibit generally satisfactory properties except that they often lack the ability to stand up to the heaviest grinding conditions and are frequently subject to severe loss of dimensional stability when heated during manufacture or use.
The present invention provides a coated abrasive that can be produced in the form of discs meeting all these desirable criteria, including dimensional stability, at a level that meets or, more often, excedes that of conventional products.
It is also an objective of this invention to provide abrasive discs that are erodable, that is to say discs that are provided with backings that can be worn away at essentially the same rate as the abrasive grains coated on the backings such that the discs can be used in angle grinding applications until the diameter of the disc has been reduced by a significant percentage, (about 10% or more), of the original diameter. This is essentially a function of the tensile strength and the isotropic character of the backing and the strength of the bond between the backing and the abrasive-containing layer.